Electric furnace.



'110.325,386.' `PAmzNlrED JULY-10, 1906. J. P. HAMMOND. ELEGTRIGFURNAGE.

APPLICATIONIILED SEPT. 18. 1905.

4 SHEETS-SHEET 1.

Ze l

PATENTED JULY 1o, 1906. J. F. HAMMOND. ELECTRIC PURNAGB. APPLICATIONFILED SEPT. 18. 1905.

4 SHEETS-SHEET 2.

Z, fw lli f A ,MJ Z f d A l Hlm W/m Yvanres:

PATENTED JULY 10, 1906.

J. E'. HAMMOND.

ELECTRIC FURNACE.

APPLIUATION FILED SEPT. 18. 1905.

'4 SHEETS-SHEET 3.

PATENTBD JULY 1o, 190m J. P. HAMMUND. ELECTRIC PURNAGB.

APPLICATION FILED SEPT. 18, 1905.

F, 'M/v,

. controlling means. Fig. Lf

UNITED STATES mini@l orrion.

Specification of Letters Patent.

Patent-.ed July 1o, 1906.

Application filed September 18,1905. Serial No. 278,854.

.To ad whom it may concern;

Be it -known that I, JonN F. HAMMOND, a citizen of the United States,residing in Brewster, in the county of Putnam and State f New York, haveinvented certain new and useful Improvements in`Electric Furnaces, ofwhich the following is a specification.

This invention relates to el ctric furnaces, and has for its obj ect torovie an improved form of meansl for app ying heat tosegregated portionsof the furnace and for so controlling the current passing through suchportions as to cause the irnnease of temperature of the furnace to bevery gradual.

A further object of the invention is to provide means whereby resultscan be attained without disastrous sparking at the various terminals.

Another object of the invention is to provide an improved form of switchor commutating device for distributingthe current through the segregatedportions of the furnace, whereby the current may be caused to passthrough such translating devices either4 in series or in multiple or inmultiple series or in various combination of such arrangements. l

In the drawings accompanying and forming' part of this specification,Figure 1 represents a front elevation of the complete device, portionsof the furnace being shown in vertical section. Fig. 2 is a sideelevation of the same. Fig. 3 is a detail ofthe switchis a plan view ofa portion of the swin ing top member, showing the pivoted switc-leverand its terminalplates mounted thereon. Fig. 5 is a view of oney of thearms of the switch-lever. Fig. 6 is a diagrammatic representation of thecommutatin device and the coils connected therewit Fig. 7-representsdiagrammatically the connections of the coils' in their successivepositions. Fig. 8 shows the relative location of the coils in themuflie. Figs. 9 to 13 show the muflle, and Figs. 14 and 15 show theinutile-switch.

The furnace comprises, essentially, a base, a frame supported on thebase, a muffle adjustably supported in the frame, and a bottom memberfor the muflle having means for moving it to'and from the muflie when inits norma position.

'mal position by means Theinvention further comprises heatin coilsvariously disposed in the interior wal s l of the muffle and a switch orccminutating device whereby the electric current can be In a suitablebase are mountedtwo up-` rights 66 67, between which is pivotallysupported the muflle, `(designated generally by. 68.) The muflie iscarried by pivotal bearings 69, whereby it can swing from its normalposition in which shownin drawings to an inverted position 68X.-(Indicated in broken lines in Fig. 2.) `It is sup orted in the nor- J o`extensions 70 of the casing of the muffle-engaging lugs 71 on theupiights -66 67. The bottom of the muflie (indicated generally byl 71")carries on each side an u iight bracket v72, provided with guide-wheelsways 7 4 in the inner sides of the uprights 66 67. By this means thebottom is movable towand `from the body of the muiie and in its upperposition will close the chamber of the muflie, as will be evident fromFig. 1.

Suitable means are provided for raising and lowering the bottom of themuffle, which may comprise a shaft 7 4', operated by crank or arm 75,and carrying a cam 76, that .engages a friction-roller 7 7, pivotedtothe bottom 71 at a central portion. By rocking this shaft the cam willraise the bottom into engagement with the muii'le and lockit in suchposition. When it is desired to use the muflie, the article tobe bakedor subjected to the heat of the mufile is placed on the bottom andthereupon the latterl raised to engage with the body of the muflie. Whenit is de- 'sired to inspect the interior of the muffle, it is onlynecessary, the bottom being in its lowered position, to turn themuii'lein its pivotal l bearings to the position-GS/Which Willpartlyinvert the same and bring the open si e uppermost. l

The top, bottom, andl four sides of the muiile have heating-coilsembedded 1n the inner walls, and the current passing through such coilsis controlled and directed bymeans of a switch or commutat'mg device.The latter device is mounted upon a plate 78, that is hinged, to theframe of the mufi'le at 79, whereby it may be 'placed in the verticalposition, as shown, or rest on the top of the muflie. It is retained inthe vertical position by suitable hooks 80.

Theswitch or commutating device is shown as cruciform, having four armsat right angles, and each arm carries a number of terminals. The 'arm Acarries six suitably-mounted spring-pins A AZ A3 A4 A5 A, all of which73, that run in `guideally connected in C-will engage the movement ofpass through and remain in contact with a bar A7. The next arm B of theswitch carries two springpins B B2, that are electric their severalpositions by the plate B3. The arm C of the switch in alinement with thearm A carries four springpins C', C3, C3, and C4, which are electricallyconnected by a plate C5. The fourth arm D carries two insulated pairs ofspring-pins, one pair D D2 remaining in engagement with 'a plate D3,while the other pair of-spring-pins E/ E? are electrically connected byengaging a plate E3. Each vof the said five plates connected with thevarious spring-pins are suitably insulated on the switch-lever, so thatthere is no connection between the pins, ,except by their respectiveplates, as just described. The switch-lever is pivoted at theintersection of its arms by a screw A3, fast on the plate 78 ofthe-furnace. To engage and coperate with the springpins on the four armsA, B, C, and D are four segregated sets of terminal blades or platesthat may be stationarily arranged on the said top member. These platesare preferably arranged in arcs concentric with the paths of movement ofthe respective spring-pins with which they contact. The pins A', A2, A3,A4, A5., and A6 will engage ,with the terminal plates 22, 21, 52, 42,34, and 54, respectively, at various stages inthe'movement of. thelever. ,The latter late 54 has three other plates" 55,1 56,I an 57 incircular alinement therewith, that are engaged by the spring-pin as willbe hereinafter set forth. The two spring-pins on the arm B will engagethe ter minal plates 25 and .26,respectively- The `four spring-pins C',C2, C3, and C4 on the arm with the terminal plates 47, 29, 37 and 50,respectively, at the various stages the switch. The two spring-pinsD andD2 will engagewith the terminal plates31 and 32, respectively, while thespring-pins E E2 will engage with the plates 4() and 39,-respectively.To 'simplify the tracing of the. current, these five msulated sets ofspring-pins will be treated as five separate insulated bars anddesignated as a, b, c, d, and e, respectively,'as if the platesconnecting the pins themselves engage the terminal blades of theswitch'.

The four sets of terminal-plates are connected with four sets or groupsof heatingcoils, which" will be designated in a general way by M, N, O,andAP. In Fig. 6 these groups are shown as each comprising two pairs ofcoils that are connected in multiple series. The current from a pair ofmains 15 and 16 enters from the positive 15 to a lead 17 to a suitableswitch 14. From thence the current passes through a conductor 18 to theblade 57, andthe latter is connected bya conductor 2Q with plate 21. Theplate 22=con nects by wire 23 withthe series of coils generallydesignated by M and consisting of coils saaaaeI m', m2, m3, and m4.After passingthrough these coils the current will pass through wire. 24to terminal-plate 25. Plate 26 connects by wire-27 with the grou N,consisting of coils 7V, n2, n3, and n3, an a return 28 connects with theplate 29. The plate 29 is connected with plate 31 by wire 30, and plate32 is connected by wire 33 with a plate 34. This latter plate connectsby `wire 35 With the group O, comprising coils o, o2, o3, arrd 04, and areturn-wire 36 from to plate 37, the latter plate beingconnected withplate 39 by wire 38. Aplate 40, disposed between the plates 32 and 39,connects by wire `41 with a plate 42. The latter plate is connected withthe group P, consisting of` coils p', p2, p3, and and a wire 44 leadsthe latter` group leads 4 from these coilsito tlgienegative lead 45. .A

wire 46 also connects the lead 45 with the plate 47. A terminal-plate 50is disposed near the plate 37 and connects by wire 51 with the saidplate 25. lAnother plate 52,

i disposed between plates 22 and 42, is connected by Wire 53 with thesaid plate 26. resistance R is shown as comprising three coils 1', 12,and plate 54 with one end of coil r', and the other end of this coil isconnectedby Wire 59 with the terminal-plate 55'. f This wire 59 isconnected to one end of the coil r2, whose other end is joined by wireLV60 with the terminalplate 56. The third coilfr3 has one end joined tothe wire 60, while its other end is connected by wire 61 with the wire18. The said four coils constituting each of the several groups M, N, O,and Pv are preferably arranged in multiple arc and are connected asfollows: Wire 23 divides and a wire coil m. From thence wire 232connects with coil m2, while the return (233)' is connected with thewire 24. The branch 241 of coil m3, while from the other end of thiscoil wire 242 leads to the coil m4, endv of this .latter .coil isconnected b wire 243with the wire 24. The wire 27 'vides and a branch271 connects with one end o`f coil n', whose other end is connected bywire 272 with coil n2. The other endof coil n? connects by wire 273 withthe wire 28`. iAnother branch 281 of the wire 27 connects with coil n3,whose other end is connected by wire 282 with coilm. The other end ofcoil n4 is connected by wire 283 with the Wire 28. The wire 36 dividesand one branch 351 connects With one end of coil-0.', whose other end isconnected by wire 352 with one end lof,"coil o2. The otherend of coil o2353 with the wire 36. The other branch 361 connects with one end of coilQ3, whose other end is connected by wire 362 with coil o3, and theotheren'd of coil o4 connects by wire 363 with the wire 3,6. one branch 431connects with one end of coil p', whose other end is connected by wire432 13. A wire 58 connects the` from the latter.

and the other v is connected wirev 231 leads to the the wire 23 connectswith the IIO ' with one end of coil p2. The other end-of.terminal-plates just referred to will be described in connection withthe course of the current in the several stages ofthe switch-lever.

- R, the plate 21 is connected with the plate 22 by a switch 62. Theseveral bars a, b, c, d, and e are represented in their normal orstarting position. The bar e being carried by the same arm as the plated will bealways in radial alinement therewith. Upon the closing of theswitch 14 the current will flow tnrough wire 18, plate 57, wire 3f),plate 21, and wire 62`- to the plate 22. Since this latter plate 22remains in contact with the switch-ban a throughout the length of itsstroke, this plate can be considered as the starting-point for tracingthe circuits in the several positions of the switch. Beginning withplate 22 the current will be seen to fioW as follows: 22,

23, M, 24, 25, b, 2e, 27, N, 23, 29, 3c, 31, d,

32, 33, 34, 35, o, 36, 37, 38, 39, e, 4o, 41, 42, 43, P, 44, 45. Upontheswitch-lever being advanced the bars a, b, d, and e willremain incontact withthe same respective plates, while the bar c will be broughtinto engagement with the plate 29 in position c2. This will have theeffectof establishing a shunt of low resistance aroundthe group of coilsO and P, which will practically cut them out. A further advance of theswitch-lever will cause the bar d to leave the plate 31 in positionrda,breaking connection between it and the plate v32, which will leave thegroups M and N in series across ithe mains, ventirely cutting out ofcircuit the groups O and P.

' The reason of first establishing a shunt around the groups() and P isto prevent sparking y when these groups are cut out of circuit by thebar d, which is effected by the bar c engaging the bar 29 before bar dleaves the late 31. These' three positions are representeddiagrammatically in Fig. 7 in the successive diagrams 1, 2 and 3,respectively. In

the first diagram it will be seen that M, N, O,

and P are arranged .in series, while in the second it will be observedthat a shuntc is established around O and P. In diagram 3 the line,` isshown as broken. between .O and a point beyond where the shunt c leadsoff from the main line, thus putting M and N in series, while O and Pare entirely cut out, and

the successive positions at the bars 0 c, and d' corresponding to thesethree diagrams are indicated by the broken line a. 0,2 a3 and c cz'c3and d d2 d3. The further advance of the switch-lever will bring the bara into engagement with plate 34, thereby connecting the If it is desirednot to use the resistance latter plate with y22, (shown at a4.) Thiswill have the effect of bringing the groups O and PV in a parallelcircuit with the groups M and N, with the result that the resistance ofthe translating devices is reduced one-half,

and hence double the current will flow, giving twice as great efficiencyas when the groups were in series. Upon the'switch-lever being advancedstill farther the bar a in position a. will contact with the strip 42,which will have the effect of establishing a shunt of low resistancearound the'group O in that branch of the circuit including the groups Oand P, as indicated in diagram 5.

'ing this breaking of the portion ofthe circuit including the group'Owill be effected with no destructive sparking. The further advance ofthe switch-lever will bring the bar c into engagement with the plate 37in position n7.

, On referring to diagram 7 it will be seen that there is still aparallel circuit, one branch including the groups M and N in series andthe current thence passing by means of the arm C to the return-Wire. Inthe other branch of the circuit thefcurrent passes first through bar a,thence through group O to `bar c and out, while a third branch of thecir cuit is established from bai` a through the group P to thereturn-wire. This will give a parallel circuit of three branches, onepassing throu h the groups M and N in series, the secon( including thegroup O, and the third passing "through the group P. The next Stage inthe operation of the switchlever, will cause the bar c to engage theplate 50 in position cg, which will have the effect of establishing yashunt of low resistance around the current in this group, as shown indiagram 8, and the farther advance of the switch-lever will cause thebar b to leave the plate 26 in position b9, thereby breaking circuitbetween this plate and the plate 25. From diagram 9 it will be seen thatthis will have the effect of entirely cutting out the group N but as thereceding`movement of the switch-lever esta lished a shunt of lowresistance around this group N there will be practically no sparkingwhen its circuit is opened. This Will'leave the three groups M, O, and Pin parallel. switch-lever will bring the' bar a into engagement with theplate 52 in position all, connecting the latter with the plate 22. g Theef- The farther advancement of the Hence the group .O will bepractically cut out of operation;

ICO

IOS

- group N, thereby practically cutting out the ar c, plate 47, vvi-re46, to the return 45.

connected the-plates' 21 and 22 the 'circuits l20, plate 5 7 ,and Wirefeet of this will be to addthe group N'inparl allel to the other groupsalready in parallel,

parallel, with the result that fourA times the current Will flow, With aconstant potential circuit, as'was flowing in the series arrange- .iment in the first position. Thefp'ath of the l current infthis positionis Ias follows: Starting Withthe plate 22 one circuit is Wire 23,` groupM, Wire 24, plate 25, Wire 51,v plate 50, other circuit isjestablishedthrough plate .22, bar c, plate 52., vWire 53, plate 26, Wire 27, groupN, Wire 28, plate 29,l bar-c, plate 47., and Wire 46 to the return 45.Another tcircuit is from plate 22, through bar'a to plate 34, Wire 35,group O, Wire 36, plate 37., bar c, plate 47, and Wire 46 -to return 45,and a fourth circuit is from bar a to plate 42, Wire 43, group P, andWire 44 to thereturn-Wire 45.

To vfacilitate the fllowing of the arms of the\lever in their successivepositions represented in the ten diagrams of Fig. 7, these positions ofthe bara are indicated onv Fig. 6 by a', a2, a3, c4, (Lilas, a, a8, a",and al, The corresponding successive positions of the "bar b from its.first osition up to vits ninth position are in icated by "the dottedlines b bzfb3 "b4 b5 1)67 bf '69. Since a't this ninth position the barb no longer bridges the plates 25 and 26, it forms no part of thecircuit in the farther advancement of the sWitch-leverland its fartherpositions need not be taken into consideration. "Similarly, thesuccessive positions of the bar c are represented by the dotted lines Vcc2 c3 c4 c5 c c7 c8 c c1". The first three positionsof the bar d areindicated by lines d', d2, and da. L In the latter position .this bar nolonger brid es the plates 3 1 and 32, and therefore in its artherositions it remains inactive and vneed not e considered". The bar e,carried bythe same arm that actuates the bar d land arranged inalinernent With the'latter, hasits positions indicated by e e2 e3 e4 e5e, Whereupon it ceases' to bridge the plates 39 and `40, and thereforeis inactive during the farther advancementof the switch-lever, and itsfar-- ther positions are of no consequence.. Inorder to prevent an undueheating ofthe 'group P, the resistance-coils R are cut in'at that stageofthe operation Where this groupfP l1s in parallel with thetWo coilsM'and N across the mains. This is effected by opening the lever 62, thatheretofore has bridge the plates21 and 22. Now as longas the bar aWould' be as-'heretofore described; but when. moved from the fourth tothe lifthposition thebara will leave Itheplate 2l, thereby cutting offYconnection between the plate 22 and the controlling-switch through theWire i While' the switch 62 was closed it establish Theleadsh 3536 eshunt ofloW-ree sistance around the'resis tically cutting them out;ynow-that switch is -open and the plate` 22 is disconnect# .wherebythefour groups will be arranged in ed from the plate 21 the only circuitleft for the current is Wire 61,'resistance`coil`r3, coil coilr, Wire58, to the plate `54, from which the current Will p/a/ss'through the arma to the -plate '22. This will have the effect .of throwing in theventire resistance R in series W1-'th the coils, in whatever 'groupingthey may be connected, as long as the bar a `engages tli'e plate 54. Thebar a will remain in engagement with the plate 54 up to and includingthe tenth position, as' indicated lin Figs. 6 .and 7, in Which latterposition, .as has been set forth, the four groups of coils are ar-'ranged in parallel series. A still farther ad vancement of 'theswitch-lever will shift the bar a vfrom the plate`54 :to the plate 55,and

by reference to Fig. 6 it will be seen that this. Will-cut out the vcoilr ofthe resistance, leaving the 'coils T2 and r3 still in series Withthe parallel arrangement of the four groups. The

next advance ofthe leverwill shift the bara from the plate 55 to lplate56,'-cutting out the coil r2, leaving Aonly the coil '13 in series withv,the said groups, 'and a s'till farther advanceFV ment of theswitch-lever to the position va13 will bring-I pla'tee57, and the latterbeing connectedwith the switch 14 bythe Wire 18 the resistancecoils willXbe `practically'cut out by a shunt of low resistance; but Vit Willbeseen in these three last positions a a12 la, the bar a :remains inengagement 22, 54, 42, and' 34, 'with which it enga in the circuit tothe four groups, land the same applies to the bar c in its'correspondingpositions c, c, and 013, it remaining in engagement with the four strips50, 37, 29, and 47. In these last four positions the barsb, d, ande areout of the circuit.

AInFig. 8 is shown the relative arrangement ofthe sixteen coilsreference to Fig. 6, but with the difference that theA respective slabsin which such coils are suitably embeddedare designated bytthe same'reference character.

front and back Aand two-end portionsfafre shown as Vcomprising tenslabs, 'there 'being with 'the same plates edinposition 10,vandftherefore .there i,s:no 'c ange` the bar a into engagement with theabove described with IIO Inithis gurethe s four side members of themutil-#that isfthe two Ain each ofthe end pJortionsandt three, rejspectively, in the 'front and -'back.portions. The top ofthe mulile isshown as composed of 'three slabs, and the bottom memberalsocontainsthrec slabs. a

pairs of leads :running tothe slabs, as shownin circuit will be 'foundto be as follows: The

which are located one in the top, one inthe IED By `following:.the'foiirv fromz-.the-commuta'tor Fig. 7, 'tothe-respecf tive sets ofcoilswith which they connectfthe back, one inftheffront, and lone inthelbottom.

connect with the four coilso located two' in the front and 44 connectwith gram 1, it will be and back, and atljird branch including thecircuit of three branches, one branch to in- `and the bottom, and athirdbranch including two in the back of the muiiie. The leads 43 the coilspp2 p3v p4, located two in each end of the muiile, and the leads 27 28connect with thefour coils n n2 nam, two or which are-located in the topofthe muflle and the other two in the bottom thereof. With thisarrangement of the heatingcoils in the mufiie byinspection of Fig.. 7,Diaseen thatL the initial position current will traverse all of saidsixteen coils. Considering next position 3, in which the groupsrepresented by O and P are cut out and the groups M and N are in circuitin series, the portions of the muiiie now energized will be one coil orslab each in the top, bottom,front, and back of the muflle, (representedby M,)V which' group will be in series with the four coils n, twolocatedy in the bottom and two in the top*that is, there are in circuitnow the three'coilsin the bottom, the three coils in the top, and oneeach in the back and front.

' In the position of Diagram 4, wherein M and N in series are connectedin parallel with O and P in series, it is evident that all of thesixteen coils are again energized; but the four groups being now inmultiple series instead of in series', as in position 1, double thecurrent will iiow through each coil and with the heating eiiectcorrespondingly augmented. In the position indicated in Diagram 6 thearrangement of the coils is similar to that of Diagram 4, except thatthe group O is now out of circuit, and hence two of the coils in thebottom and likewise two coils in they front" are out of circuit. Sincein this position the four coils represented by P -that is, ythe twoends-are connected in parallel with the other eight coils, and thereforewill receive a greater strength of current, a suitable resistance R isintroauced into the circuit to prevent overtafxing these end coils. ,Inthe position of Diagram 7 there will be a parallel clude' the top coilsandthebpttom coils and one coil each in the` front and back, a secondbranch including two coils each in the front coils in the ends.Intheosition of Diagram 9 there will be a aral el circuit -of` threebranches, one branc includin one coil each in the top, bottom, front,and ack, a second branch including two coilsl eachA in the top thecoilsjin the ends. In'the position of Diaram 10, having a .parallelcircuit of four branches, each ofthe said groups M, N, O, and P will beinparallel, and therefore all of the coils Willfbe 1n circuit and four'timesthe uantity, of current will be assin thi-ou h- (tlhemfas assedthroughin t e posltion :in icated in Diagram 1.

The bottom of the' mufle being movable,

the resistance R and the leads.

it sconnected with leads carried by` the Vuprightsand connectedtofourljointed links 8 1 l connected between the bottom an]` a separating-plate82, fast on the uprights. I hese latter serve to convey the current tothe two circuits of the bottom, and n3 and n4 being in series andrequiring but one pair of leads, the .Other pair connecting m2. Suitableflexible leads connect with the other portionsof the muiiie and alsowith the several terminal plates on the switchboard.

. If the switch-lever or commutator were reversed-that is, movedbackward from any of its positionsfit would produce disastrous resultsunless the circuit were first opened at the switch 14 or'some othersuitableplace. To prevent such efi'e'ct, there is provided 'alocking-rack 83, movably carried by a strip 84, hinged along one of itslongitudinal edges to the edge of the base-plate 78, which is in thehandle portion of the switch-lever. The strip 84 has two screws 85passing through suitable slots in the rack, permitting the latter toslide into and out of position o en agement with'the switch-arm. It isyiel ably retained in such position by a spring 86. The switch-lever-orcut-out 14 has an arm 14a arranged to engage the bent end 841 of thestrip 84 when the switch is' opened, as indicated in broken lines inFig. 3. Such movement of the switch will rock the strip on its hingedconnection withthe switch-plate 78 and swing the rack 83 out of positionof engagem t-with the switch-lever, permitting the latter to return toits initial position; but it is evident that the rack will not be movedto such position except when the switch 14 1s opened, cutting out ofcircuit to the terminals ofthe commutator.

For convenience in referring specifically to four translating members ofany type or form whatsoever', in the' claims a, b, c, and d will be usedto designate such translating devices or groups of translating devices,it being under- 'stood that such designating characters do not referspeciiically to the'our oups of heating-coils hereinbefore referre to,but to any form of a translating device or group of translating devices.

In order to able bod of the muflie with the wires on the stand, a'Aour-blade switch is provided on each side. (Shown separately in Figs. 14and 15.)

An insulating-block 87is fast onI the frame at each side, and eachblockcarries four separate blades 88, connected, respectively, withv.An'insulating-block 89is secured Qn eachside of the hinge portion thatis secured tol the mufiie-body, and on each of these'blocks is arrangedfour separate blades 90, arranged to engage the respective blades 88'when the mule-body 1s in its normal positiong'asshown in Figs. 2 and13;`but upon the mu'e-body bein swung to the open 'position these bladesl dlsengage, as indicated Fig. 15.

l In Figa to 13 is shown the arrangement IOO electrically connect themov- 'insertion of strips s.

of ,the slabs or blocks constituting the main portion of the muffle.Fig. 9 is a side elevation of the blocks with the outer frame removed.Fig. 10 is a vertical section through the same. Fig. 11 is a plan viewof the bottom member of the mufHe; and Fig. 12 is a transverse verticalsection, the latter iigure showing the frame supporting themuffle-slabs. The body portion ofthe muffle comprises a metal framework91, comprising a top and four sides that may be integral-or separate andsecured together in any preferred manner. The vertical side slabs 92have at each end a' projecting rib 92at extending along the end. At theouter face of each block there is a strip 92b extending along itsintermediate portion and projecting at each end beyond the end portionof the block, forming at such portion a channel 92C. At each of the fourcorners are located blocks 93, having the outer edges adjoining theblocks 92 phanneled at'93EL and have ribs 93b at the :top and bottom.Strips 94 are inserted' between the projecting portions of the 'sideblocks and also that of the end pieces 93, thereby serving to breakjoints with the adjoinin edges of the slabs. The frame 91 has inwarly-projecting portions 91a, that project under the lower ends oftheblocks 92 and 93, with the ribbed portions 91b extending upward in thechannel 92c of the blocks, thereby supporting the'side members andretaining .them in position. The top members of the mufiie are formed ofthree slabs 95, that have theirouter edges channeled at 95a for theinsertion of strips 96, servin tol break joints `at the edges of theslabs. A each end. of the topportion is a slab 97', having a projectinportion 97 a extending over the adj acent s ab to break joint therewith.The top ribs 92- and 931 'of the vertical slabs extend into suitablechannels 971?, and a packing, such as asbestor iiber, is arrangedbetween the rib and the channeled portion to effectually close such'joints abndfprevent 'escape of' .heatL The bottom portion of the-muffle in which are supported the bottom slabs. The latter colmpristhree transverse slabs 99, having their lower adjacent edgespchannele'dfor the 100, `serving to' fclose the At each end of 'the botjoints ofthe sla tom is a slab 101, havin a portion 1,02 pro-" jectinglunderneaththe a jacent slab to break joint t erewith. The top face of the slabs101 isv lower than that of the three intermediate slabs, and a channeledportion is provided, at the ends of the intermediate slabs, forming arectangular 'channel extending around -the4 top of f the ebottom slabs.An additional channel 103 is also formed in this rectangular the Vprojecting ribs along channeled lportionfor the reception o the bottomportions of the side members that extend into this chanagement with thebody portion of the mufe. A suitable packing, such as asbestos fiberfisplaced in this channel to insure a' e said portions of the.

plurality of groups, and a commutator arranged' to connect withvtheterminals of said groups of coils; said terminalsand commutator beingarranged whereby said groups will position o f the commutatorsaid-groups will be connected in parallel, and in all positions of thecommutator between said positions more ofsaid groups.

2. l`In an electric furnace, the combination of a munie having a top anda bottom and side members, each of said portions of the muiie Vbeingprovided with heating coils, said'coils being connected by leads into aplurality of groups; 'and a commutator arranged to connect with groupsof coils; said terminals and commutator being arranged whereby saidgroups will first be connected in the advancement of sets of such ity'of groups arranged in series, will be disposed in parallel; at a stillfurther advanced position of the commutator all of said groups thecommutator two tions ofthe commutator between said series position andsaid parallel 'position circuit-will be established through one or moreofsuch groups.

" 3. In an electric furnace, the combination of a 'muflie provided withside members and a top and a bottom, electric coils arranged in each ofsaid portions ofthe Inuiiie an electric switchcomprising a commutator,and a set of terminals connected with said coils of the mufiie;A saidcoils being divided into four groups, one grou of coils a the top,bottom, ont and back of the muffle; a second group of coils b comprisingcoils dis-v Lposed in the bottom and top of the muiiie; a third group ofcoils c comprising oils. disposed 1n thefront and bacloof the muflie,and a fourth group comprising coils disp nals being arranged tor wherebycircuit will first be established through all of the groups in series;at a fur-` ther stage in the advancement ofthe commutator the'grous'will be connectedin multiple series, at a stil further advancedposition of the commutator all of -said groupswill be 'raised intoeniirst b e connected in series,- at an advancedcircuit will beestablished through one Yor groups, each containing a pluralwill bedisposed in parallel; and in all posi-I u osed in' the two other sidesof the muffle; said termirelative to the commutathe commutator betweensaid series positions the terminals of said i in series; at afurtherstage IJOO iro

being disposed in l connected in parallel, and inkall positionsv of I'SOand lsaid parallel position circuit will be established through one ormore of such groups,

' 4. In an electric furnace, the combination of a muflie provided withside members and a top and a bottom, electric coils yarranged in each ofsaid portions of the-muiiie,-an electric switch comprising a commutator,and a set of terminals connected with said coils of the mutlie; saidcoils being divided into four groups, one group of coils a beingdisposed in the top, bottoni, front and back of the muflie a secondgroup of coils b comprising coils disposed in the bottom and top of themuffie; and a third group'ot1 coils c comprising coils disposed in thefront and back of the mullie; and a fourth group comprising coilsdisposed in thetwo other sides of thojmulie; and a commutating Adevicearranged to connect with the terminals of the translating members, saidterminals and commutator being arranged whereby said groups will irst beconnected in series, at an advanced osition `of the commutator saidmembers Wil be connected in parallel, and in all positions of thecommutator between said positions circuit vwill be established throughone or more of said translating members'.

5. In an electric furnace, the combination of a-mulie provided with foursides and a too and a bottom, electric coils arranged in eac of said sixportions of the mufle, an electric switch comprising a commutator, and aset of terminals connected with said coils of the muffle, said coilsbein divided into four groups, one grou."v of cois a being disposed inthe top, bottom, ront and back of the muile; a second group of coils bcomprising coils disposed in the bottom and top of the muie; athirdgroup of coils c comprising coils disposed in the front and back ofthe mufHe and a fourth group comprising coils .disposed in the two othersides of the muiiie; said terminals being arranged whereby the saidgroups will irst be connected in series, and in the successive positionsof advancement of the commutator the latter Iwill so connect theterminals of the groups whereby in the second osition av shunt oflowresistance will be es'talilished around two of such groups as c andd; in the third position of the commutator said groups. gand `d will beout leaving groups a and b in circuit;in the .fourth position oftheicommutator groups@ and b in series will bconnected in parallel withgrou s c and d in series; the fifth position 'of t e commutator a shuntof low resistance will be established around group c in the said lattermultiple-series arrangement; in the sixth position the groups aand binserieswill lbeconnect'ed lparalel with the grou' d; in the seventhposition the groups a, an b connected in series will be connected inparallel with group c and alsqo with group d; in the eighth position ashunt of low resistance will be established around the group b in thesaid seventh position; in the ninth position the groups a, c and d willbe connected in parallel; and in the tenth position the four groups u,b, c and el will be connected in parallel.

6. In an electric furnace, the combination of a muflie having a top anda bottom and four sides, each of such six portions being provided withheating-coils, a switch device comprising terminals connected with saidcoils and a commutator; said terminals being arranged and connected withcoils wherebyin the first position of the switch said coils will bedivided into four groups and such groul s will be connected in series,at an advanced position of the commutator one group of coils`includingthe to bottom, front and back of the inutile, will be connectedin'series with another group including coils in the to and bottom of themuffle; at a still further a vanced position of the commutator twogroups of coils as a and b in series will be connect'ed in parallel withtwo other groups or" coils as c and el also connected in series, the`i'irst group c including coils disposed in the top, bottom, front andback of the muiie, the second group b including coils disposed in thetop and bottom of the mufiie, the third group c comprising coilsdisposed in the front and back of the muflie, and the fourth group dcomprising coils disposed in the two end portions of thi` muile; at astillfurther advanced .position two groups of coils will be connected inseries iol" which one group includes coils disposed in the top, bottom,front and back of the 'mutiia and the other group includes coilsdisposed in the top andbottom of the mufl'le, 1n the said latterposition, a third group of coils also being connected in parallel withsaid two groups of coils,said third group including coils disposed inthe end portions ofthe mufile at a still further advanced position ofthe commutator three groups of TOO coils will be connected in parallel,one group l including coils ldisposed ini/the end portions of themufile, the second group including coils disposed in the front and theback of the muflie,` and the third of said parallel groups comprisingtwo sets of coils in series, of which latter one set includesjcoilsdisposed in the top, bottom, front and back ofthe mufHe, and

the other set including coils disposed in thev 'tpip and bottom of themuiie at astill further a v anced position of the commntator threegroups of coils will be connected in series, one group comprising coilsarranged in the top, bottom, front and back of the-muflie, another saidgroup comprising coils disposed in the bottom and top of the muffle, andthe third of said lattergroups including coils disposed in the endportions of the muflie and at a still further advanced position of thecommutator four groups of coils will be connected inseries, one 'groupcomprising coils disposed in the top, bottoml front and back of themuiile,

I'Io

another group comprising (coils disposed in the bottom and top of themufile, another cured to the frame, and switch-blades ser rou comprisingcoils disposed in the front nd ack of the muiile and they fourth groupcomprising coils disposed in the end portions ofthe mufl'le. t I

' 7. In an electric furnace, the combination of a muflie'havingits foursidi andtop permanentlygclosed, a frame ony which the mufe is mounted, apivoted joint between the mufle and the frame whereby the muffle can beinverted from its normal osition, a bottom member for the mufle, andmeans carried by the frame for raising and lowering thebottom member toclose the muiiie, the latter including means for locking thebottom whenengaging thevmuffie. i

8. The combina-tion with the ir-me supporting the inutile-bottom, and.the muffle- .body pivoted thereon, of switch-blades secured to themufie-body and arranged to engage with said blades respectively `whenthe muf'le-bcdy is swung on the frame. n

9. The combination with the muiiie-body supported on a frame,`of'abottom member vertically movable in said frame to engage the body memberand close its bottom, rolli `ers connected with the bottom'member andguided in said frame, a cam member arranged to reciprocate the bottommember, and a handle-lever A.arranged to control said cam.

10. In a muffle, the combination oa supporting-frame having a top andside portions, inwardlyprojectingparts atthe lower parts of the sideportions, vertical slabsengaging 'the side portions and supported bysaid 1nwardly-ezrtendingparts, strips breaking .joints withthe sideslabs, slabs extending across the top and resting on the side slabs,strips breaking joints with said slabs at their upper portions, thewsideslabs having ribs projecting upwardly at their top portions, .the tophaving channeled portions into which said ribs project, packing locatedbetweenI said ribs and the channeled portions, and a bottom membercomprisin A a frame and slabs arranged to engage the ody member. i

1.1.1111 a mue, the combination of a-Asup-v i breaking j bottom slabs'havin s25,see

portin -frame having a top and side portions, mwar ly-projecting partsat the lower parts of the side portions, vertical slabs engaging theside portions and supported, by said inwardly-extending parts, stripsbreaking joints with' the side slabs, slabs ,extending across the topand resting on the side slabs, strips breaking joints upper portions,the side slabs having ribs projecting upwardly at their top-portions,the top having channeled portions into which said ribs project, packinglocated'between said ribs and the channeled portions, and a bottommember comprisin a pan-shaped frame having slabs exten ing "across theframe, strips at thevbottom portions of the slabs breaking jointstherewith, said slabs having a rectangular channel adjacent the edges,ribs rojecting vdownwardly from the said side slabs arranged to entersaid channel when the .bottom and 'body members are brought together,and suitable packing ar- .ranged between said` ribs and the channelportion.

y, 12. In a mufiie, 'the combination of a frame comprising a frame andside portions, the side portions having' ,inwardly-projecting plates at`the lower part, the vertical side slabs 92 provided with the projectingstrip portions 92h, the channels 920, and the ribbed portions 92a, thecorner-blocks 93 provided with the channeled portions 93a, and theribbed portions 93", the top slabs 95 and 97 with said slabs at theirhaving thefstrips 96 breaking joints therewith, :and having arectangularchannel portion` engaging the said ribs of the side membersthe bottom portion of the muffle comprising 99 and' a pan-shaped framehaving thev slabs 191 located therein,'the strips 102 the channelportion 102 cooperating with te said ribs on the side members, and.suitable packing located in said channeled portions.

. l JOHN F. Harmom.

Witnesses: I i

y 'SAMUEL R. BARTON, v

oint with the bottom slabs, the

